MPs have backed raising the legal age of marriage to 18 to stop vulnerable children being forced to wed.
In England and Wales, parental consent is needed for 16 and 17-year-olds, while others take part in non-registered marriages at younger ages.
But Tory MP Pauline Latham said this allowed children to be coerced into unions that could damage their lives.
She wants to make all marriages and civil partnerships under 18 illegal, including religious or cultural ones.
MPs backed Mrs Latham’s Marriage and Civil Partnership (Minimum Age) Bill unopposed.
She told the Commons it would create a blanket ban on marriage for under-18s in England and Wales and send “a clear message to everyone that child marriage is unacceptable”.
The government is supporting her bill as it goes through the Commons – with Health Secretary Sajid Javid having played a major part in the proposal.
He told MPs the plan was “an opportunity for this House to show unambiguously and make it crystal clear that child marriage is child abuse and it will never be tolerated in this country”.
The bill was widely welcomed by campaign groups – but some minority groups want further consultation on the plan.
The current law in England and Wales means people can get married at 18 or, with parental consent, at 16 or 17.
But there is no law against religious or cultural ceremonies which are not registered with local councils taking place under this age.
Mrs Latham warned that some children were being made to marry as young as seven without any legal consequences for the adults involved – with figures from charity Karma Nirvana showing 76 known cases of child marriage in England and Wales in the last 12 months alone.
And even those with registered weddings at 16 and 17 could be forced into them when fully reliant on the adults around them – leaving them more open to domestic abuse and damaged life chances, she added.
“This is about breaking a harmful practice legacy that is often handed down from generation to generation,” Mrs Latham said.
“This bill will be an incredibly important tool in safeguarding young people and giving them the best chance for their futures.”
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Under the new law, children would not face penalties, but adults could face up to seven years in jail and a fine for facilitating the marriage.
This would include adults who took children abroad to carry out the marriage.
But Ms Latham said the bill would also help the UK live up to its international obligations.
“We are asking other countries to stop child marriage and they can easily turn around to us and say why should we, you do it,” she added.
“By supporting this bill we are helping the UK to set an example to the rest of the world in prioritising children’s futures.”
Analysis
By Rajdeep Sandhu, BBC Westminster correspondent
It’s not often, but there are moments like this when MPs in the Commons widely agree on an issue.
There was very little disagreement about changing the law to protect those at risk of forced child marriage.
But what’s prompted the government to support it? Many have been campaigning for years on this issue.
Could it have been the influence of Health Secretary Sajid Javid, who previously raised the issue while on the back benches? It can be much easier to affect change when you know the right people to talk to.
The government has also made clear it wants to be a moral leader on this issue globally, and criminalising marriage under 18 sends a clear message.
But this doesn’t apply to Northern Ireland and Scotland, where the minimum age will stay at 16 – in Northern Ireland you still need parental consent to marry at 16, but in Scotland you don’t.
It will undoubtedly add pressure for change and to bring everywhere in the UK into line with international standards.
The proposal – which was debated in the Commons on Friday and will now continue its process through Parliament to become law – has cross-party support.
Labour’s Virendra Sharma said his own mother was made to marry at 16, and while she was “kind and clever woman”, it had stopped her from getting an education.
“Her gift to her daughters, my sisters, was to offer them access to education,” he said. “Not to marry them off young, but instead to encourage school and university before settling down.
“Marriage under 18 is child marriage [and is] not something we would condone in any other situation.”
His Labour colleague, Sarah Champion, said the bill was not about race, religion, or even the institution of marriage, but about child protection.
She felt “shame” for not recognising when her own friend – a white British girl who had married a much older white American man at 16 – was a victim of child marriage
“They were both religious, I won’t say religious extremists, they were both very fundamental in their religious beliefs,” she said.
“He was very aggressive. He was very abusive. I vividly remember him pinning her down in front of me and spitting in her face, saying: ‘It is your duty to obey me, God says you have to obey me’. I just couldn’t believe it.”
‘The root causes’
Conservative Selaine Saxby echoed statements that child marriage was tantamount to child abuse, adding: “You can’t make your will until you’re 18, you can’t serve on a jury, you can’t come and be an MP until you’re 18, yet you’re allowed to get married.
“You can’t even get a tattoo until you’re 18, so it is surprising… marriage is a serious undertaking and one that is not to be ventured into lightly.”
But some communities have raised concerns about the criminalisation element of the bill.
The chief executive of the Traveller Movement, Yvonne MacNamara, said while her organisation agreed in principle with the age rise, “criminalisation tends to drive problems underground” and failed to address “the root causes”.
She also warned the bill could have “the perverse, if unintended, consequence of increasing the number of children – particular European Roma and Traveller children – being taken into care”.
Ms MacNamara urged the government to have an “open dialogue with affected groups” going forward, saying: “Meaningful consultation is vital.”
In a statement, Justice Secretary Dominic Raab said: “Forced child marriage ruins lives. We back this bill to keep vulnerable young people safe, by raising the legal age of marriage to 18, and closing gaps in the law which leave them at risk.”